Mayor de Blasio spends hours at a time on the telephone seeking counsel from liberal confidants like Rev. Al Sharpton, union boss George Gresham, political consultants Valerie Berlin and Jonathan Rosen, and top aides to Bill Clinton, a well-placed Democratic insider told The Post.

“He’s obsessively taking their temperature. He does obsessive calls that are long-winded in a way that’s not really productive to the city,” said the source, who has witnessed Hizzoner’s yakfests firsthand. “He’s engaged, but he’s not proactively making the city run. I just don’t think the guy has it in him.”

Upon his return from an eight-day vacation to Italy, de Blasio gabbed an hour with Gresham, president of the 1199 SEIU health-care workers union, so he could better gauge public opinion on the tragic choking death of Eric Garner, who died in Staten Island at the hands of a cop trying to arrest him for selling untaxed cigarettes.

The two also weighed the pros and cons of allowing Sharpton to stage a protest march across the Verrazano-Narrows Bridge.

When de Blasio phoned Sharpton, “there was a lot of pleading on the mayor’s end,” the source said.

Other long-winded calls are nothing more than political bull sessions — and a way for the mayor to procrastinate from doing his job, the source said.

“Show me his proposal for the hottest issue in the city right now, reforming the Police Department,” the source said. “Show me his proposal for reforming what’s going on with low-wage workers in the city. When was the last time he was in Staten Island?”

“It just adds up to a lonely man in his office on his headset. It’s remarkable to look at.”

Many of the mayor’s City Hall chats last for more than an hour, according to the source.

“The mayor has only so much bandwidth,” the source added. “This isn’t the best use of it.”

Rosen denied that he or fellow consultant Berlin engaged in “these types of conversations” with the mayor, but declined to say how long a typical phone call lasts with Hizzoner.

De Blasio spokeswoman Emma Wolfe dismissed the source’s claims, but also declined to provide any detail about his calls.

“The mayor’s priorities and his time are right where they ought to be,” she said.